This invention relates to an ink jet head having a plurality of nozzles for discharging ink supplied thereto from an ink supplying part, and more particularly to an ink jet head suitable for use, for example, as a printing head of an ink jet printer and a printing apparatus which includes the ink jet head.
FIGS. 33 and 34 are views illustrating a configuration of a conventional ink jet head (the official gazette of Japanese Patent Laid-Open No. 148921/1995), and wherein FIG. 33 is an exploded perspective view showing a configuration of essential part of the ink jet head and FIG. 34 is a vertical sectional view showing a configuration of essential art of the ink jet head.
As shown in FIGS. 33 and 34, the conventional ink jet head includes a pressure generation unit 320 and a flow path unit 340.
The pressure generation unit 320 includes a communication path substrate 301, a pressure chamber formation substrate 302 and a diaphragm 304 and is formed such that the diaphragm 304 is adhered to one face side (upper side in FIGS. 33 and 34) of the pressure chamber formation substrate 302 and the communication path substrate 301 is adhered to the other face side (lower side in FIGS. 33 and 34) of the pressure chamber formation substrate 302.
A plurality of portions which serve as pressure chambers 303 are formed by punching in the pressure chamber formation substrate 302, and a plurality of communication paths 309 for communicating the pressure chambers 303 of the pressure chamber formation substrate 302 and ink supplying paths 314 formed in an ink supplying path formation substrate 313, which is hereinafter described, with each other are formed by perforation in the communication path substrate 301. Further, a plurality of nozzle communication holes 318a are perforated in the communication path substrate 301 in a corresponding relationship to the pressure chambers 303 of the pressure chamber formation substrate 302.
A plurality of pressure elements 306 are disposed on the face (upper side in FIGS. 33 and 34) of the diaphragm 304 opposite to the face adhered to the pressure chamber formation substrate 302 in a corresponding relationship to the pressure chambers 303 of the pressure chamber formation substrate 302 with lower electrodes 305 interposed therebetween. Further, upper electrodes not shown are formed on the opposite side (upper side in FIGS. 33 and 34) of the pressure elements 306 to the lower electrodes 305.
The flow path unit 340 includes a reservoir chamber formation substrate 312, an ink supplying path formation substrate 313, and a nozzle formation substrate 311. The ink supplying path formation substrate 313 is adhered to one face side (upper side in FIGS. 33 and 34) of the reservoir chamber formation substrate 312 and the nozzle formation substrate 311 is adhered to the other face side (lower side in FIGS. 33 and 34) of the reservoir chamber formation substrate 312.
A plurality of nozzles 316 are formed in the nozzle formation substrate 311. A V-shaped ink reservoir chamber 315 is formed by a technique such as punching in the reservoir chamber formation substrate 312, and nozzle communication paths 318c are perforated at positions of the reservoir chamber formation substrate 312 corresponding to the nozzles 316 formed in the nozzle formation substrate 311.
A plurality of ink supplying paths 314 for communicating and connecting the ink reservoir chamber 315 and the communication paths 309 of the communication path substrate 301 with and to each other are formed in the ink supplying path formation substrate 313. Further, nozzle communication paths 318b are perforated at positions of the ink supplying path formation substrate 313 corresponding to the nozzle communication paths 318c formed in the reservoir chamber formation substrate 312. Furthermore, an opening 317 for communicating and connecting an ink tank not shown and the ink reservoir chamber 315 with and to each other is formed in the ink supplying path formation substrate 313.
The pressure generation unit 320 and the flow path unit 340 are adhered to each other by a bonding agent or the like. Consequently, as shown in FIG. 34, the nozzle communication paths 318a of the communication path substrate 301, the nozzle communication paths 318b of the ink supplying path formation substrate 313 and the nozzle communication paths 318c of the reservoir chamber formation substrate 312 are communicated with the nozzles 316 formed in the nozzle formation substrate 311. Further, the pressure chambers 303 and the ink reservoir chamber 315 are communicated with each other through the ink supplying paths 314 and the communication paths 309.
In the configuration described above, ink supplied from the ink tank not shown is supplied into the ink reservoir chamber 315 through the opening 317 and further supplied into the pressure chambers 303 through the ink supplying paths 314 and the communication paths 309.
Then, driving signals are supplied to the upper electrodes (not shown) and the lower electrodes 305 from a driving circuit not shown to deform the pressure elements 306 thereby to displace the diaphragm 304 to raise the ink pressure in the pressure chambers 303 so that drops of the ink are discharged from the nozzles 316 through the nozzle communication holes 318a to 318c to form an image on a recording medium.
In such a conventional ink jet head as described above, while ink is supplied from the ink tank not shown to the ink reservoir chamber 315 through the opening 317, since the opening 317 must be formed with a greater size as the amount of ink consumed by the ink jet head increases, it is required for the opening 317 to have a greater opening area as the number of nozzles 316 formed in the nozzle formation substrate 311 increases. Consequently, the conventional ink jet head has a subject to be solved that the degree of integration of the ink jet head cannot be raised and, since the ink jet head cannot be miniaturized, a high production cost is required as well.
Meanwhile, in order to improve the print quality of the ink jet printer, it is necessary to make the ink jetting characteristic from the nozzles 316 uniform. In order to make ink jetting from a nozzle 316 on the upstream side and another nozzle 316 on the downstream side along an ink supplying path uniform, stabilized ink supply is required, and it is necessary to lower and make the fluid resistances of the ink supply paths for the individual nozzles to ink uniform.
In the conventional ink jet head described above, in the substrates which form the ink jet head, the ink reservoir chamber 315 for supplying ink supplied thereto from the opening 317 into the pressure chambers 303 is formed, and the pressure chambers 303 are communicated with and connected to the ink reservoir chamber 315 through the ink supplying paths 314 and the communication paths 309.
Generally, in order to miniaturize an ink jet head, it is a common practice to form it with a reduced thickness. However, in order to lower the resistance to ink in the ink reservoir chamber 315, the supplying path length for ink must be reduced and the sectional area must be increased. Accordingly, it is necessary to make the sectional shape of the ink reservoir chamber 315 wide. Consequently, also this gives rise to a subject to be solved in that improvement of the degree of integration and/or miniaturization of the ink jet head are obstructed and a high production cost is required as well.
The present invention has been made in view of such subjects as described above, and it is an object of the present invention to devise the shape and so forth of an ink supplying path to each pressure chamber to make the ink supply to the pressure chambers uniform and make it possible to raise the degree of integration of an ink jet head thereby to miniaturize the ink jet head and hence a printing apparatus.
In order to attain the object described above, according to the present invention, an ink jet head having a plurality of nozzles for discharging ink supplied thereto from an ink supplying part is characterized in that it comprises a head body member including a plurality of pressure chambers provided individually for the nozzles for being filled with the ink and a plurality of pressurization elements provided individually for the pressure chambers for pressurizing the pressure chambers to discharge the ink in the pressure chambers from the nozzles, that an ink staying space for temporarily staying the ink from the ink supplying part therein is formed between the head body member and the ink supplying part, and that a plurality of ink supplying paths for communicating the ink staying space and the plurality of pressure chambers individually with each other are formed in the head body member such that one end side of each of the ink supplying paths is open to the ink staying space on an outer face of the head body member and the other end side of each of the ink supplying paths is open to a corresponding one of the pressure chambers.
Further, according to the present invention, a printing apparatus which includes an ink jet head having a plurality of nozzles for discharging ink supplied thereto from an ink supplying part is characterized in that the ink jet head comprises a head body member including a plurality of pressure chambers provided individually for the nozzles for being filled with the ink and a plurality of pressurization elements provided individually for the pressure chambers for pressurizing the pressure chambers to discharge the ink in the pressure chambers from the nozzles, that an ink staying space for temporarily staying the ink from the ink supplying part therein is formed between the head body member and the ink supplying part, and that a plurality of ink supplying paths for communicating the ink staying space and the plurality of pressure chambers individually with each other are formed in the head body member such that one end side of each of the ink supplying paths is open to the ink staying space on an outer face of the head body member and the other end side of each of the ink supplying paths is open to a corresponding one of the pressure chambers.
With the ink jet head and the printing apparatus of the present invention, since the ink staying space and the pressure chambers are communicated with each other individually by the ink supplying paths, ink from the ink supplying part can be supplied directly into the pressure chambers, and there is no necessity to provide ink supplying ports for exclusive use in the head body member. Therefore, there is an advantage that the degree of integration of the ink jet head can be improved and the ink jet head and hence the printing apparatus can be miniaturized, which contributes also to reduction of the production cost. Further, there is an advantage that supply of ink to the pressure chambers can be made uniform, and the printing quality can be improved.
A framework member may be provided in a projecting manner on the head body member in such a manner as to surround openings of the plurality of ink supplying paths on the outer face of the head body member, and the ink staying space may be formed by the framework member, head body member and ink supplying part. With the configuration, there is an advantage that the rigidity of the head body member can be raised and the ink staying space can be formed readily.
The head body member may be formed on a substrate, and the framework member may be formed as a remaining portion of the substrate on the head body member by partly removing the substrate from the head body member. With the configuration, there is an advantage that, since the framework member can be formed readily and with certainty in a process of formation of the substrate, the production cost can be reduced.
The framework member may be used as a joining element for joining the ink supplying part to the head body member. With the configuration, the ink supplying part can be joined readily and with certainty to the head body member. Further, also where the ink supplying part is adhered to the head body member using a bonding agent or the like, since there is no possibility that protruding bonding agent or the like may stick to a pressurization element or the like of the head body member, there is no necessity to form an adhesive width on the head body member. Consequently, there is an advantage that the degree of integration of the ink jet head can be raised.
Each of the pressurization elements may include a diaphragm which forms one face of a corresponding one of the pressure chambers and partitions the pressure chamber and the ink staying space from each other, and a piezoelectric element formed by lamination on the diaphragm on the outside of the pressure chamber for driving the diaphragm to pressurize the pressure chamber. With the configuration, there is an advantage that the pressurization elements can be formed with certainty and the readiness of production of the ink jet head can be improved.
Each of the ink supplying paths may extend through the diaphragm in a region other than a region in which a corresponding one of the piezoelectric elements is laminated. With the configuration, since the ink is prevented from contacting with the piezoelectric elements, there is an advantage that there is no possibility that the piezoelectric elements may be influenced by the ink.
Alternatively, each of the ink supplying paths may extend through the diaphragm in a region in which a corresponding one of the piezoelectric elements is laminated. With the configuration, since there is no necessity to provide a space for exclusive use for openings of the ink supplying paths, there is an advantage that the degree of integration of the ink jet head can be further improved and the ink jet head and hence the printing apparatus can be further miniaturized, which contributes to further reduction of the production cost.
Further alternatively, each of the ink supplying paths maybe formed so as to open on a face of a corresponding one of the pressure chambers other than the face formed by the diaphragm, or each of the ink supplying paths may be formed so as to open on a face of a corresponding one of the pressure chambers opposing to the face formed by the diaphragm. With the configuration, since the pressurizing elements of the pressure chambers are not influenced by the openings at all, there is an advantage that the rigidity of the pressure chambers can be maintained and besides the pressurization operation of the pressure chambers is stabilized.